This invention relates to threshing and separating machines and more particularly to stone traps used in such machines.
Stone or rock traps are generally old and well known in the art. This is because of the damage stones can cause if they reach the threshing and separating area of such a machine. One type of stone trap presently used on commercial combines incorporates a trap door pivotally mounted to an overload release latch. The trap door is preferably located in the front portion of the concave under the threshing cylinder. When a stone enters the concave its weight trips the overload release latch causing the trap door to open and eject the stone to the ground. This type of stone trap has several limitations. Due to the tolerances inherent in this type stone trap, only larger stones, six inches or more in diameter, are detected and ejected. Smaller stones proceed into the threshing area causing damage to both the cylinder and the concave. Further, the vibrations inherent in this type of machine (i.e. a combine) prematurely disengage the release latch thereby opening the trap door causing a portion of the crop material to fall to the ground prior to entering the threshing and separating area. This inadvertent opening of the trap door can severely increase the total percentage of grain loss during the harvesting operation.
It is, therefore, the purpose of this invention to provide a stone trap for a threshing and separating machine which will eliminate the limitations discussed hereinabove.